Plastic expansion water tank

The utility model discloses a plastic expansion water tank, which belongs to the technical field of medium-heavy-duty truck parts. The technical scheme is that the plastic expansion water tank is characterized by comprising an expansion water tank body, wherein the expansion water tank body is formed by welding an upper casing with a lower casing; reinforcing ribs are arranged inside the expansion water tank body 1; a filling chamber and an expansion chamber are arranged in the expansion water tank and are arranged in parallel from front to back; an overflow channel hole for overflowing to the expansion chamber is formed in the top of the filling cavity; a siphon channel communicated with the overflow channel hole is arranged in the expansion chamber; the other end of the siphon channel is arranged at the bottom of the expansion chamber. The plastic expansion water tank disclosed by the utility model has the beneficial effects of simple and compact structure, convenience and practicality; the control over the cost of a finished vehicle and the reduction of environmental pollution are facilitated; the reliability of an assembly is high, higher pressure can be maintained under higher temperature for a long time, and a filling cover can effectively prevent the falling; the occupied space distributed on the finished vehicle is smaller and pipelines are compact, so that the reduction of the dead weight and the cost of the finished vehicle is facilitated.